Add RenderObject.childCount

sky/sdk/lib/rendering/object.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'dart:sky' show Point, Size, Rect, Color, Paint, Path;
 
 import '../base/hit_test.dart';
 import '../base/node.dart';
@@ skipping 349 matching lines @@
       assert(nextSibling != this);
       assert(nextSibling.parentData.previousSibling == this);
       nextSibling.parentData.previousSibling = previousSibling;
     }
     previousSibling = null;
     nextSibling = null;
   }
 }
 
 abstract class ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType extends ContainerParentDataMixin<ChildType>> implements RenderObject {
-  // abstract class that has only InlineNode children
 
   bool _debugUltimatePreviousSiblingOf(ChildType child, { ChildType equals }) {
     assert(child.parentData is ParentDataType);
     while (child.parentData.previousSibling != null) {
       assert(child.parentData.previousSibling != child);
       child = child.parentData.previousSibling;
       assert(child.parentData is ParentDataType);
     }
     return child == equals;
   }
   bool _debugUltimateNextSiblingOf(ChildType child, { ChildType equals }) {
     assert(child.parentData is ParentDataType);
     while (child.parentData.nextSibling != null) {
       assert(child.parentData.nextSibling != child);
       child = child.parentData.nextSibling;
       assert(child.parentData is ParentDataType);
     }
     return child == equals;
   }
 
+  int _childCount = 0;
+  int get childCount => _childCount;
+
   ChildType _firstChild;
   ChildType _lastChild;
   void _addToChildList(ChildType child, { ChildType before }) {
     assert(child.parentData is ParentDataType);
     assert(child.parentData.nextSibling == null);
     assert(child.parentData.previousSibling == null);
+    _childCount += 1;
+    assert(_childCount > 0);
     if (before == null) {
       // append at the end (_lastChild)
       child.parentData.previousSibling = _lastChild;
       if (_lastChild != null) {
         assert(_lastChild.parentData is ParentDataType);
         _lastChild.parentData.nextSibling = child;
       }
       _lastChild = child;
       if (_firstChild == null)
         _firstChild = child;
@@ skipping 34 matching lines @@
   }
   void addAll(List<ChildType> children) {
     if (children != null)
       for (ChildType child in children)
         add(child);
   }
   void _removeFromChildList(ChildType child) {
     assert(child.parentData is ParentDataType);
     assert(_debugUltimatePreviousSiblingOf(child, equals: _firstChild));
     assert(_debugUltimateNextSiblingOf(child, equals: _lastChild));
+    _childCount -= 1;
+    assert(_childCount > 0);
     if (child.parentData.previousSibling == null) {
       assert(_firstChild == child);
       _firstChild = child.parentData.nextSibling;
     } else {
       assert(child.parentData.previousSibling.parentData is ParentDataType);
       child.parentData.previousSibling.parentData.nextSibling = child.parentData.nextSibling;
     }
     if (child.parentData.nextSibling == null) {
       assert(_lastChild == child);
       _lastChild = child.parentData.previousSibling;
@@ skipping 64 matching lines @@
     int count = 1;
     ChildType child = _firstChild;
     while (child != null) {
       result += '${prefix}child ${count}: ${child.toString(prefix)}';
       count += 1;
       child = child.parentData.nextSibling;
     }
     return result;
   }
 }